Tower Six

Tower Six was found by exploring and is located northwest of Deepshore. It has a large 6 on the front, and is made primarily out of gold. It's made to be a giant computer and is used to control life along with the other towers. Its specific use is unknown, though its purpose as an observation deck was confirmed in a QnA. It was accessed by IntelligentMan during the Invasion. Niklos was questioned about Tower 6, and he had this to say about it: "Well tower 6 isn't real. It's theoretical. I...nevermind. Speaking too much." It was later revealed that Niklos was not aware of the Tower's existence when he spoke to players. However, IntelligentMan's accessing of the Tower during the event implys that

IntelligentMan accessing Tower Six during the Invasion

it existed at the time. This means that either the Tower was constructed without Niklos' knowledge or that the scientist is feigning ignorance.